I do not know if this is the right topic but i have a question.
When I am home then i have NC 12 running on linux mint 18.2 KDE 64-bit, when i playback some video then some extentions are not supported. MP4 is fine but MKV or AVI are not.
However, When i am away and access the UI then the video playback is as normal. (this is on a windows pc).
What should i install on linux to get it supported?
Nextcloud version (eg, 10.0.2): 12.0.2
Operating system and version (eg, Ubuntu 16.04): Linux Mint 18.* 64 bit
Apache or nginx version (eg, Apache 2.4.25): Apache
PHP version (eg, 5.6): 7.*
Is this the first time you’ve seen this error?: No
Can you reliably replicate it? (If so, please outline steps):
Just playback a video other then MP4
Which file format is supported for playback totally depends on the browser you’re using.
You could try the same browser on Mint that you use on Windows for viewing MKV and AVI files - hoping that the browser has the same video file support on unix like it has on Windows.
Edit: oh, missed the point that you are using Firefox on both systems. I agree with JimmyKater: then the codecs are probably missing on Mint.